Information Technology Reference
In-Depth Information
at half-duplex mode, and the resulting duplex mismatch results in poor performance and port errors.
Remember, if you set speed and duplex on one side, you must set speed and duplex on the connecting
device as well to avoid these problems.
To view the port status after setting the speed and duplex, use the
show port
command.
Switch-A (enable)
set port speed 2/1 100
Port(s) 2/1 speed set to 100 Mbps.
Switch-A (enable)
set port duplex 2/1 full
Port(s) 2/1 set to full-duplex.
Switch-A (enable)
show port
Port Name Status Vlan Level Duplex Speed Type
----- ------------------ ---------- ---------- ------ ------ ----- ------------
2/1
full
100
10/100BaseTX
connected 1
normal
...
The timing results are as follows:
Switch-A (enable)
show time
Fri Feb 25 2000, 14
0528
Eastern
Switch-A (enable)
set port enable 2/1
Port 2/1 enabled.
Switch-A (enable)
2000 Feb 25 14
0529
Eastern -0500 %PAGP-5-PORTTOSTP:Port 2/1 joined bridgeport 2/1
2000 Feb 25 14
0530
Eastern -0500 %SPANTREE-6-PORTFWD: port 2/1 state in vlan 1 changed
to
forwarding
.
The final result gives a time of 2 seconds (0528 to 0530).
Step 11
We did another visually timed test (watching our watches) by starting a continuous
ping
(
ping -t
)
directed to the switch on a PC attached to the switch. We then disconnected the cable from the switch.
The
ping
s started failing. Then we reconnected the cable to the switch and checked our watches to see
how long it took for the switch to respond to the
ping
s from the PC. It took about 5 or 6 seconds with
autonegotiation for speed and duplex turned on, and about 4 seconds with autonegotiation for speed and
duplex turned off.
A lot of variables are involved in this test (PC initialization, PC software, switch console port responding
to requests, and so on), but we just wanted to get some feel for how long it would take to get a response
from the PCs point of view. All the tests were from the switches' internal debug message point of view.
How to Reduce Startup Delay on the Catalyst 2900XL/3500XL Switch
The 2900XL and 3500XL models can be configured from a web browser, by SNMP, or by the
command-line interface (CLI). We will use the CLI. The following is an example of viewing the
spanning-tree state of a port, turning on PortFast and then verifying that it is on. The 2900XL/3500XL
does
support EtherChannel and trunking, but it
does not
support dynamic EtherChannel creation (PAgP)
or dynamic trunk negotiation (DTP) in the version that we tested (11.2[8.2]SA6), so we have no need to
turn them off in this test. Also, after turning on PortFast, the elapsed time for the port to come up is
already less than 1 second, so there is not much point in trying to change speed/duplex negotiation
settings to speed things up. We hope that 1 second will be fast enough! By default, PortFast is off on the
switch ports. The commands to turn on PortFast are discussed next.
